Zoltán Kodály
L'Accorche-Choeur, Ensemble vocal Fribourg
Veni, Veni Emmanuel is a synthesis of the great "O Antiphons" that are used for Vespers during the octave before Christmas (Dec. 17-23). These antiphons are of ancient origin and date back to at least the ninth century.

Veni Domine et noli tardare, by Francisco Guerrero (composer), with animated score.
FAQ:
Q: Who is Francisco Guerrero (composer)?
A: A Spanish composer of the Renaissance. You can read more about him here: http://en.wikipedia.org/wiki/Francisco_Guerrero_(composer)
Q: What do the colors mean?
A: Each pitch class has its own color, chosen by mapping the musician's "circle of fifths" to the artist's "color wheel". I choose C to be blue. This is YouTube user Smalin's invention. You can read more about it here: http://www.musanim.com/mam/pfifth.htm
Q: How did you make this animation?
A: With a program I wrote in Python. I also used FFMPEG, SoX, TiMidity, FluidSynth, Python Image Library, and midicsv. All excellent, free, open-source software.
Q: Could you make a video of this other song?
A: Sure! Well, maybe. For copyright reasons, it has to be public domain music. Just comment below, or send me a message and I'll see what I can do.